In Quantum Physics the Spin of an elementary particle is defined to be an „intrinsic, inherent“ property. The same to the magnetic moment (μ) due to the spin of charged particles - like Electron (me) and Proton (mp). So the intrinsic spin (S=1/2h-bar) of the electron entails a magnetic moment because of charge (e). However, a magnetic moment of a charged particle can also be generated by a circular motion (due to spin) of an electric charge (e), forming a current. Hence the „orbital motion of charge“ around a „mass-nucleus“ generates a magnetic moment by Ampère’s law. This concept leads to an alternative way calculating the neutrino mass (mν) while discussing the beta decay of a neutron into fragments: proton, electron, neutrino and binding Energy. The change of neutrons magnetic moment during the decay process based on energy and spin and charge conservation allows to calculate the restmass of the neutrino: mν = 0.10(20)eV.